Temperature sensor circuit

ABSTRACT

A temperature sensor circuit implemented in electronic circuitry that senses the temperature at a site, digitizes the sensed temperature, and then outputs a signal representing such a sensed temperature. The temperature sensor circuit converts a voltage signal that is proportional to the temperature to a first digital value. The temperature sensor circuit converts a voltage signal that is inversely proportional to the temperature to a second digital value. The sensed temperature is determined as a function of a difference between the first and second digital values.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. Patent Application Ser. No.14/258,629, which is hereby incorporated by reference herein.

TECHNICAL FIELD

The present invention is related in general to a temperature sensorcircuit, and in particular, to a temperature sensor circuit implementedwithin electronic circuitry.

BACKGROUND INFORMATION

It has become increasingly important to monitor temperatures withinelectronic circuitry (e.g., on an integrated circuit (“IC”) die, orchip). For example, it is important to manage the on-die temperature ina multi-core SOC (“system on chip”) due to issues pertaining to thepositive feedback mechanism associated with leakage current andtemperature, in that leakage current results in increases in temperaturewithin the die circuitry. A temperature sensor can be used to monitorthe temperature of an electronic component, such as a CPU (“centralprocessing unit”), GPU (“graphics processing unit”), MPU(“microprocessor unit”), SOC (“system on chip”), etc. When thetemperature exceeds a predetermined threshold, the temperature sensorcan alert circuitry to slow down (or even shut down) the electroniccomponent to reduce power consumption, and thus reduce the temperatureso that overheating that can cause destructive failure to the electroniccomponent may be prevented.

Typically, temperature sensors include a reference circuit andtemperature measuring circuitry, wherein the temperature dependency iseither proportional to absolute temperature (“PTAT”), wherein themeasuring circuit outputs a voltage that increases in proportion to arise in temperature at the location of the electronic circuitry in whichthe temperature sensor is located (i.e., has a positive temperaturecoefficient), or complementary to absolute temperature (“CTAT”), whereinthe measuring circuit outputs a voltage that decreases in proportion toa rise in temperature at the location of the electronic circuitry inwhich the temperature sensor is located (i.e., has a negativetemperature coefficient). Further, DAC (“digital-to-analog converter”)based temperature sensors have been implemented relying on comparing aPTAT voltage and a CTAT base-emitter voltage. This approach, however,has suffered from DAC code-to-temperature non-linearity issues; that is,such temperature sensors cannot achieve good linearity over a widetemperature range, resulting in poor temperature measurement accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary plot showing relationships of PTAT andCTAT voltages to temperature.

FIG. 2 illustrates an exemplary plot showing a temperature conversionusing PTAT and CTAT voltages.

FIG. 3 illustrates exemplary electronic circuitry configured inaccordance with embodiments of the present invention.

FIG. 4 illustrates a temperature sensor circuit configured in accordancewith embodiments of the present invention.

FIG. 5 illustrates electronic circuitry for conversion of a sensedtemperature to voltage value(s).

FIG. 6 illustrates an exemplary circuit layout of a remote temperaturesensor.

FIG. 7 illustrates a flow diagram of a process for determining atemperature of a location (site) within electronic circuitry inaccordance with embodiments of the present invention.

DETAILED DESCRIPTION

Aspects of the present invention essentially provide a temperaturesensing circuit or process implemented on electronic circuitry thatsenses the temperature at a location (site) within the electroniccircuitry, and then outputs a signal representing such a sensedtemperature based on a difference between PTAT and CTAT voltagesproduced as a function of the sensed temperature.

FIG. 1 illustrates an exemplary plot showing the relationships of PTATand CTAT voltages to temperatures (e.g., operating temperatures ofelectronic circuitry (e.g., in an integrated circuit) in which atemperature sensor circuit configured in accordance with embodiments ofthe present invention would be implemented). As will be furtherdisclosed herein, circuitry within the temperature sensor circuitoutputs a voltage (for a fixed current) that increases in proportion toa temperature rise or has a positive temperature coefficient, within aportion of the overall electronic circuitry in which a temperaturesensor circuit is implemented. Such a temperature dependency is referredto as being proportional to absolute temperature (“PTAT”). Thetemperature sensor circuit will also produce a voltage that drops inproportion to a temperature rise, or has a negative temperaturecoefficient, within the electronic circuitry being measured, and isreferred to as the complementary to absolute temperature (“CTAT”)voltage. The exemplary plot of FIG. 1 illustrates how the PTAT voltage(noted herein as “V_(PTAT)”) increases from a first voltage V1 to asecond voltage V2 as the temperature increases from a first temperatureT1 to a second temperature T2, and how the CTAT voltage (noted herein as“V_(CTAT)”) decreases as the temperature increases from the firsttemperature T1 to the second temperature T2.

It can be seen from FIGS. 1 and 2 that the difference, ΔV, between theV_(PTAT) voltage and the V_(CTAT) voltage (i.e., V_(PTAT)−V_(CTAT)),linearly increases with increasing temperature (the term ΔV also isreferred to herein as the difference voltage or the difference voltagevalue). Thus, the difference between V_(PTAT) and V_(CTAT) can be usedto represent the temperature of a location on a semiconductor integratedcircuit because it has a linear function directly proportional totemperature. Moreover, the ΔV has a higher mV/° C. (approximately 3 mV/°C.) compared to that of V_(PTAT) (approximately 2 mV/° C.). Therefore,the temperature can be measured with greater accuracy due to the largerdifference in voltage per degree.

As further described with respect to FIG. 5, embodiments of the presentinvention essentially provide PTAT and CTAT generation circuitry,wherein the PTAT voltage generation circuitry is used to also generatethe CTAT voltage, so that the PTAT and CTAT voltages track each other.As depicted in FIG. 2, embodiments of the present invention then utilizedifferences between the PTAT and CTAT voltages as a direct measure ofthe temperature that is being sensed within a portion of the electroniccircuitry in which the temperature sensor circuit has been implemented.In embodiments of the present invention, a single PTAT voltage is usedfor the reference across the entire temperature range.

FIG. 3 illustrates a simplified block diagram of an exemplary electronicsystem (also referred to herein as “electronic circuitry”) 300 in whicha temperature sensor circuit configured in accordance with embodimentsof the present invention has been implemented. The electronic system 300may comprise any type of electronic component, such as a CPU, GPU, MPU,SOC, etc. As shown, N temperature sensors 304, individually numberedtemperature sensor 1, temperature sensor 2, . . . temperature sensor N(in which N is any positive integer greater than 0) are distributed inthe system 300. Each temperature sensor 304 is implemented in proximityto the location of its corresponding “site” for determining thetemperature at that location within the electronic system 300, anddevelops a corresponding temperature sense signal S1 . . . SN providedto the temperature measurement select and control block 302. Thetemperature measurement select and control block 302 accesses andactivates a selected one or more of the temperature sensors 304 fordetermining and outputting a temperature at the corresponding one ormore locations (sites).

The electronic system 300 may be implemented on an integrated circuit(“IC”) die or chip, or as part of an embedded processing system, or thelike. In this case, the multiple temperature sensors 304 may beimplemented to determine the temperatures at corresponding locations onthe chip. Although multiple temperature sensors 304 are shown, N mayalso be 1 for a configuration with only one temperature sensor 304.Alternatively, the electronic system 300 may be implemented in adiscrete manner in which the temperature measurement select and controlblock 302 and the one or more temperature sensors 304 are eachimplemented on a separate IC, or otherwise may include any combinationof one or more ICs or semiconductor chips, or the like. The electronicsystem 300 may be configured for any type of application, such ascommunication systems, computer systems, sensing devices, etc., and forany one or more of consumer, industrial, commercial, computing, orautomotive fields.

FIG. 4 illustrates a block diagram of a temperature sensor circuitconfigured in accordance with embodiments of the present invention. Forpurposes of describing embodiments of the present invention, FIG. 4shows the temperature sensors 304 as part of a designated local unit401, the reason of which will be more apparent in the discussion of FIG.5 hereinafter. The temperature measurement select and control block 302includes a PTAT/CTAT generation circuit 410, which produces the V_(PTAT)and V_(CTAT) voltages as a function of a temperature sensed by one ormore of the remote temperature sensors 304.

As will be further described with respect to FIGS. 5 and 7, thePTAT/CTAT generation circuit 410 receives a temperature sensor sitecontrol signal, SITE_SEL, from the control logic 418. The V_(PTAT) andV_(CTAT) voltages (also referred to herein as voltage signals) are sentto the multiplexers 403 and 404. The control logic 418 will send aninput selection signal, MUX_SEL, to the multiplexers 403 and 404 tofirst select the V_(PTAT) voltage to be transmitted through themultiplexer 403 to the analog-to-digital converter (“ADC”) 405 and theV_(CTAT) voltage to be sent to the ADC 406. As is well-known, ananalog-to-digital converter is a device that converts a continuousphysical quantity (e.g., a voltage, or voltage signal) to a digitalnumber (e.g., N binary bits) that represents the quantity's amplitude.Thus, the ADC 405 and the ADC 406 convert the received voltage signalsto respective digital versions thereof, i.e., digital (e.g., binary)values of N bits (where N is a positive integer). Thus, the V_(PTAT)voltage is converted to a digital version thereof, digital valueD_(PTAT), by the ADC 405, while the V_(CTAT) voltage is converted to adigital version thereof, digital value D_(CTAT), by the ADC 406. Thesedigital values, D_(PTAT) and D_(CTAT), are then sent by the ADC 405 andthe ADC 406, respectively, to the multiplexers 407 and 408. Since thecontrol logic 418 has selected the first (e.g., “0”) input for themultiplexers 403, 404, 407, and 408, these digital values, D_(PTAT) andD_(CTAT), will be output to the subtraction circuitry 409, whichproduces a difference voltage value, D_(PTAT)-D_(CTAT), between the twodigital values D_(PTAT) and D_(CTAT) for output to the control logic418. This digital version of the difference voltage value ΔV is thenused to determine the operating temperature of the sensed locationwithin the electronic circuit.

As will be further described hereinafter, embodiments of the presentinvention produce another, or second, iteration of the digital bitvalues for purposes of alleviating or mitigating potential conversionerrors inherent in the analog-to-digital converters. However,embodiments of the present invention are not limited to requiringproduction of two or more such iterations of the digital bit values, andas such do not require implementation of the multiplexers. Furthermore,the multiplexers 407 and 408 are implemented in embodiments of thepresent invention in order that the digital values D_(PTAT) and D_(CTAT)are sent into the same inputs into the subtraction circuitry 409 foreach of the iterations. However, the subtraction circuitry 409 may beconfigured in embodiments of the present invention so that it canreceive the digital values D_(PTAT) and D_(CTAT) into any of its inputsand still properly function for producing the difference voltage valueD_(PTAT)−D_(CTAT).

It is well known that analog-to-digital converters are subject to offsetand gain errors resulting from variations in the reference voltage,V_(REF), utilized to power the ADC. The temperature independentreference voltages utilized in previous temperature sensor circuits weregenerated by using bandgap circuitry. These circuits requirecharacterization and trimming (i.e., adjustments) to account for thevariations during fabrication, which involves additional costs.Therefore, having a reference voltage that is not accurate but can beused to measure the temperature is desirable.

Embodiments of the present invention alleviate or mitigate such problemsassociated with a floating reference voltage since the differencebetween the PTAT and CTAT voltages is utilized for determining thetemperature of the selected temperature sensor site within theintegrated circuit. In other words, as indicated in FIG. 1, for aparticular value of the reference voltage, V_(REF), the difference, ΔV,in the PTAT and CTAT voltages remains constant regardless of thevariations in the reference voltage. This can be seen in the fact thatthe difference voltage ΔV is equal to(V_(PTAT)−V_(REF))−(V_(CTAT)−V_(REF)), where V_(REF) represents thecommon reference voltage utilized by (energizing) the ADC 405 and theADC 406. Thus, changes in value (magnitude) of the reference voltage,V_(REF), resulting from changes in temperature does not affect the valueof the difference voltage ΔV. If the reference voltage, V_(REF),increases (e.g., from its mean operating value), the digital value ofV_(PTAT) (i.e., D_(PTAT)) will decrease, and similarly the digital valueof V_(CTAT) (i.e., D_(CTAT)) will decrease, resulting in the differencein the digital values, D_(PTAT)−D_(CTAT), remaining the same. Similarly,if the reference voltage, V_(REF), decreases (e.g., from its meanoperating value), the digital value of V_(PTAT) (i.e., D_(PTAT)) willincrease, and similarly the digital value of V_(CTAT) (i.e., D_(CTAT))will increase, resulting in the difference in the digital values,D_(PTAT)−D_(CTAT), remaining the same. As a result, a temperatureindependent reference voltage source(s) for energizing theanalog-to-digital converters is not needed in embodiments of the presentinvention. Therefore, in embodiments of the present invention, any oneor more of the ADC 405 and the ADC 406 are energized by a referencevoltage source(s) that outputs a reference voltage that fluctuates inmagnitude as a function of temperature.

Furthermore, offset and gain errors associated with analog-to-digitalconverters can be further alleviated or mitigated by the multiplexing ofthe V_(PTAT) and V_(CTAT) voltage signals, in accordance withembodiments of the present invention. In other words, as furtherdescribed hereinafter with respect to FIG. 7, the control logic 418 willthen select the second (e.g., “1”) inputs to the multiplexers 403, 404,407, and 408 to determine another, or second, iteration of the D_(PTAT)and D_(CTAT) digital values, whereby the ADC 405 now converts theV_(CTAT) voltage signal into its digital version thereof, digital valueD_(CTAT), while the ADC 406 now converts the V_(PTAT) voltage signalinto its digital version thereat digital value D_(PTAT). This seconditeration of the difference value of the D_(PTAT) and D_(CTAT) digitalvalues is also calculated by the subtraction circuitry 409 for output tothe control logic 418, which then averages the two iterations of thedifference values.

FIG. 5 illustrates further details regarding the circuitry utilized toimplement the local unit 401 and the PTAT/CTAT generation circuit 410,in accordance with embodiments of the present invention. Depicted withinthe local unit 401 in FIG. 5 is a temperature sensor site 304. Thistemperature sensor site 304 may be selected from the N temperaturesensors 304 shown in FIG. 3 by the SITE_SEL signal received bymultiplexers 501, 502, and 503, which are coupled to each of the Ntemperature sensors 304.

In embodiments of the present invention, a differential bipolar junctiontransistor (“BJT”) diode array may be utilized to sense the temperatureat a selected temperature sensor site 304, instead of utilizing a singleBJT diode array. As a result, as further described hereinafter, aΔV_(be) voltage value is generated instead of merely relying upon asingle voltage value of V_(be).

FIG. 6 illustrates an exemplary circuit layout of a remote temperaturesensor site 304 implemented on a die or chip, in accordance withembodiments of the present invention. Diode Q_(R) has a significantlysmaller diode area than the diodes Q_(N) . . . Q_(N1) surrounding diodeQ_(R). The base emitter voltage V_(be) is a function of current density,which is a function of the device's emitter injection area. Embodimentsof the present invention utilize the ratio of the injection areas of theemitters between the diodes Q_(R) and Q_(N) . . . Q_(N1). Diode Q_(R)may be comprised of one or more BJT diodes, and Q_(N) . . . Q_(N1) maybe comprised of two or more BJT diodes, but regardless, the totalinjection area of the parallel connected diodes Q_(N) . . . Q_(N1) isgreater than the injection area for the diode(s) Q_(R). Note that thedevice layout illustrated in FIG. 6 is merely exemplary. In thisillustrated example, there are nine diodes Q_(R) shown surrounded bythirty-four diodes Q₁ . . . Q₃₄. Any number of the diodes Q_(R) may beactivated for utilization in a temperature sensor site 304, with theinactive diodes acting as “dummies.” The same may be true with respectto the diodes Q₁ . . . Q₃₄, which are shown surrounded by one or more“rings” of dummy devices. Dummy devices may operate as a means forsignal buffering/separation from adjoining devices on the die or chip.

A device layout as shown in the exemplary layout in FIG. 6 provides thepreviously noted ratio of emitter injection areas for a temperaturesensor site 304. It is this ratio of emitter injection areas thatenables the generation of the ΔV_(be) value, in accordance withembodiments of the present invention. As temperature increases at thetemperature sensor site 304, the base to emitter voltages of the BJTdiodes decreases. However, the base-emitter voltage for the voltageV_(be1) from the parallel arrangement of the diodes Q_(N) . . . Q_(N1)is generally less than the base-emitter voltage V_(be0) from diode Q_(R)for a given temperature, because the emitter current density is lower.Moreover, this difference linearly increases with increasingtemperature; thus, the ΔV_(be) value increases with temperature.

Alternatively, the temperature sensors 304 may be configured utilizingPN junction diodes, diode-coupled PNPs, NPN transistors, or the like.

Returning to FIG. 5, a first current mirror is created by thecombination of the transistors (e.g., p-channel field effect transistors(“PFET”)) M1, M2, and an operational amplifier 504 in order to have thecurrents I₀ and I₁ mirror each other. The current I₀ is created by thebase-emitter voltage V_(be0) from diode Q_(R), while current I₁ iscreated by the base-emitter voltage V_(be1) from the parallelarrangement of diodes Q_(N) . . . Q_(N1).

As shown in FIG. 5, once a temperature sensor 304 at a location isselected, voltages V_(be0) and V_(be1) (which adjust, or vary, as afunction of the operating temperature at the location) are sensed by thePTAT/CTAT generation circuit 410. The operational amplifier 504functions to maintain as equal its input voltages V_(a) and V_(b). SinceV_(a)=V_(be0), then V_(b)=V_(be0). ΔV_(be) is the voltage drop acrossthe resistor R_(Vbe), which is equal to V_(b)−V_(c). V_(c) is equal toV_(be1). Therefore, ΔV_(be) is equal to V_(be0)−V_(be1). Since thecurrents I₁ and I_(PTAT) are forced to be the same, the PTAT voltagesignal, V_(PTAT), produced through resistor R1 is proportional toΔV_(be).

The outputs of multiplexers 502 and 503 are providing the same voltageV_(be1), which is therefore input as voltage V_(c) into the negativeinput of the operational amplifier 505; the positive input of theoperational amplifier 505 receives the voltage V_(d). The second currentmirror configured from the operational amplifier 505 and the transistors(e.g., PFETs) M4 and M5 produces the current I₂ running through resistorR2, which produces the ICAT current, I_(ICAT), which produces the CTATvoltage signal, V_(CTAT), through resistor sR2. Thus, the CTAT voltagesignal, V_(CTAT), is proportional to voltage V_(be1).

As a result of the foregoing, the PTAT voltage signal, V_(PTAT), isproportional to increases in temperature at the location of the selectedtemperature sensor 304, while the CTAT voltage signal, V_(CTAT), isinversely proportional to temperature increases at the location of theselected temperature sensor 304. Furthermore, the configuration of thePTAT/CTAT generation circuit 410 results in the V_(PTAT) and V_(CTAT)voltage signals tracking each other.

Embodiments of the present invention for performing the foregoing willnow be described with respect to FIG. 7, with further reference to FIGS.4 and 5. All or a portion of the process 700 may be implemented in thecontrol logic 418. In step 701, the control logic 418 initiatestemperature monitoring, for example, in response to an externallygenerated signal, such as from a user or another process running on theIC chip (e.g., electronic system 300) on which an embodiment of thepresent invention is implemented, or in response to an automatically orintermittently generated internal signal (e.g., generated by a processimplemented within the control logic 418) to monitor the temperature atone or more of the temperature sensor sites 304.

In step 702, the control logic 418 determines which of the temperaturesensor sites 304 it selects to monitor next, and sends the SITE_SELsignal to the multiplexers 501, 502, and 503 in order that the voltagesof diodes Q_(R) and Q_(N) . . . Q_(N1) at the selected temperature site304 are sensed. A result is the generation of the V_(PTAT) and V_(CTAT)voltage signals by the PTAT/CTAT generation circuit 410, as previouslydescribed with respect to FIG. 5.

As previously noted, in step 703, the control logic 418 will send aMUX_SEL signal to the multiplexers 403, 404, 407, and 408 to select thefirst (e.g., “0”) inputs to these multiplexers. This will result in theADC 405 converting the V_(PTAT) voltage signal it receives at its inputfrom the output of the multiplexer 405 to the digital version of theV_(PTAT) voltage signal, which is the D_(PTAT) digital value, which willthen be selected by the multiplexer 407 for output into the subtractioncircuitry 409. This will also result in the V_(CTAT) voltage signalbeing converted by the ADC 406 to the digital version of the V_(CTAT)voltage signal, which is the D_(CTAT) digital value, which is selectedby the multiplexer 408 for input into the subtraction circuitry 409. Thesubtraction circuitry 409 will then produce a digital version of thedifference voltage value, ΔV, which is equal to the difference betweenthe D_(PTAT) and D_(CTAT) digital values, i.e., D_(PTAT)−D_(CTAT). Thesubtraction circuitry 409 may be comprised of any well-known circuitryfor producing a difference value from inputted digital values. Forexample, subtraction circuitry 409 may be implemented with a digitaladder circuit, whereby the subtraction is performed by adding the 1'scomplement of one input to the other input, resulting in a subtractedvalue between the two inputs (e.g., D_(PTAT) and D_(CTAT)).Alternatively, a 2's complement method may be used for the subtractioncircuitry 409. Both of the 1's and 2's complement methods forsubtraction of digital, or binary, numbers are well-known in the art.

In step 704, this first digital version of the difference voltage value,ΔV, is received by the control logic 418 (this first digital version ofthe difference voltage value, ΔV, is also referred herein as the firstiteration of the difference voltage value). In step 705, the controllogic 418 will then use the MUX_SEL signal to select the second (e.g.,“1”) inputs for the multiplexers 403, 404, 407, and 408. This willresult in the ADC 405 digitizing the V_(CTAT) voltage signal to producea second iteration of the digital version of the V_(CTAT) voltagesignal, D_(CTAT), which is selected by the multiplexer 408 for inputinto the subtraction circuitry 409. Likewise, this will also cause theV_(PTAT) voltage signal to be digitized by the ADC 406 to produce asecond iteration of the digital version of the V_(PTAT) voltage signal,D_(PTAT), which will be selected by the multiplexer 407 for input intothe subtraction circuitry 409. In step 706, this second iteration of thedifference voltage value, ΔV, from the subtraction circuitry 409 willthen be received by the control logic 418.

In step 707, the control logic 418 will average the received first andsecond iterations of the difference voltage value, ΔV. In step 708, thecontrol logic 418 will output the temperature of the location of theselected temperature sensor 304 as a function of the average of thefirst and second iterations of the difference voltage value, ΔV. Thiscorresponding temperature may be determined in various manners. Forexample, when the IC chip (electronic system 300) is being manufactured,each of the temperature sensor sites 304 can be intentionally heated toone or more specifically known temperatures. These one or morespecifically known temperatures can then be utilized in the process 700to generate a lookup table. For example, a first ΔV can be determined ata first temperature for the temperature sensor site; then a second ΔVcan be determined at a second temperature for that temperature sensorsite; then, using a straight line equation calculation, the operatingtemperatures for all ΔV measurements can be computed (as shown in theexemplary plot in FIG. 2) and inserted in the lookup table. Theresultant lookup table stored in the control logic 418 will thus includea unique ΔV for each corresponding temperature.

Another manner in which to determine the temperature to output in step708 is to produce a corresponding straight line fitting equation thatmay be implemented in software or hardware in the control logic 418,which will then be utilized to output the temperature as a function ofthe measured ΔV.

The digital versions of the previously disclosed voltage signals mayalso be processed by a digital filter technique to remove any noise dueto the utilized non-standard voltage references. Such digital filteringmay be implemented with a simple averaging technique, a moving areatechnique, a fancy Kalman filtering technique, or any other equivalenttechnique.

Aspects of the present invention disclose a system for determining atemperature of a location in electronic circuitry, in which the systemincludes first circuitry, in proximity to the location in the electroniccircuitry, configured to adjust first and second output voltages as afunction of an operating temperature of the electronic circuitry at thelocation; second circuitry configured to convert the first and secondoutput voltages to a first voltage signal that is proportional to theoperating temperature; third circuitry configured to convert the secondoutput voltage to a second voltage signal that is inversely proportionalto the operating temperature; fourth circuitry configured to determine adifference between the first voltage signal and the second voltagesignal to produce a difference voltage value; and fifth circuitryconfigured to determine the temperature of the location in theelectronic circuitry as a function of the difference voltage value. Thesecond circuitry may include a first current mirror circuit with a firstinput coupled to receive the first output voltage from the firstcircuitry and a second input coupled to receive the second outputvoltage from the first circuitry, wherein the first current mirrorcircuit is configured to convert a difference between the first andsecond output voltages into the first voltage signal that isproportional to the operating temperature. The third circuitry mayinclude a second current mirror circuit with a third input coupled toreceive the second output voltage from the first circuitry, wherein thesecond current mirror circuit is configured to convert the second outputvoltage into the second voltage signal that is inversely proportional tothe operating temperature. The first circuitry may include a first setof one or more diodes having a first emitter injection area, the firstset of the one or more diodes configured to output the first outputvoltage; and a second set of one or more diodes having a second emitterinjection area, the second set of the one or more diodes configured tooutput the second output voltage, wherein the second emitter injectionarea is greater than the first emitter injection area. The fourthcircuitry may include circuitry configured to produce a first digitalversion of the first voltage signal; circuitry configured to produce asecond digital version of the second voltage signal; and circuitryconfigured to produce a digital version of the difference voltage valuefrom a difference between the first digital version of the first voltagesignal and the second digital version of the second voltage signal,wherein the temperature of the location in the electronic circuitry isdetermined as a function of the digital version of the differencevoltage value. The circuitry configured to produce the first digitalversion of the first voltage signal may include a firstanalog-to-digital converter, wherein the circuitry configured to producethe second digital version of the second voltage signal may include asecond analog-to-digital converter, and wherein the circuitry configuredto produce the difference voltage value may include subtractioncircuitry configured to receive the first and second digital versions.The first and second analog-to-digital converters may be energized by acommon reference voltage. The fourth circuitry may further include afirst multiplexer with a first input configured to receive the firstvoltage signal that is proportional to the operating temperature, and asecond input configured to receive the second voltage signal that isinversely proportional to the operating temperature, wherein an input ofthe first analog-to-digital converter is coupled to an output of thefirst multiplexer. The fourth circuitry may further include a secondmultiplexer with a first input configured to receive the second voltagesignal that is inversely proportional to the operating temperature, anda second input configured to receive the first voltage signal that isproportional to the operating temperature, wherein an input of thesecond analog-to-digital converter is coupled to an output of the secondmultiplexer. The fourth circuitry may further include selectioncircuitry configured to sequentially select the first and second inputsto the first and second multiplexers in order to respectively producefirst and second iterations of the difference voltage value. The fifthcircuitry may be configured to determine the temperature of the locationin the electronic circuitry as a function of an average of the first andsecond iterations of the difference voltage value. The fourth circuitrymay further include a third multiplexer with a first input coupled to anoutput of the first analog-to-digital converter, a second input coupledto an output of the second analog-to-digital converter, and an outputcoupled to a first input of the subtraction circuitry; and a fourthmultiplexer with a first input coupled to an output of the secondanalog-to-digital converter, a second input coupled to an output of thefirst analog-to-digital converter, and an output coupled to a secondinput of the subtraction circuitry, wherein the selection circuitry isconfigured to sequentially select the first and second inputs to thefirst, second, third, and fourth multiplexers in order to produce the atleast first and second iterations of the difference voltage value.

Aspects of the present invention disclose a method for determining atemperature of a location in electronic circuitry, in which the methodconverts a first voltage signal that is proportional to the temperatureof the location in the electronic circuitry to a first digital value.converts a second voltage signal that is inversely proportional to thetemperature of the location in the electronic circuitry to a seconddigital value, determines a first difference value between the first andsecond digital values, and outputs the temperature of the location inthe electronic circuitry as a function of the first difference valuebetween the first and second digital values. In aspects of the method,the first voltage signal that is proportional to the temperature of thelocation in the electronic circuitry is a difference between the firstand second voltages. The converting of the first and second voltagesignals may be performed with first and second analog-to-digitalconverters energized with a common reference voltage. Aspects of themethod may further convert the first voltage signal that is proportionalto the temperature of the location in the electronic circuitry to athird digital value, convert the second voltage signal that is inverselyproportional to the temperature of the location in the electroniccircuitry to a fourth digital value, determine a second difference valuebetween the third and fourth digital values, and output the temperatureof the location in the electronic circuitry as a function of an averageof the first and second difference values.

Aspects of the present invention disclose a system for determining atemperature of a location in electronic circuitry, in which the systemincludes a first set of circuit elements configured to output a firstoutput voltage; a second set of circuit elements configured to output asecond output voltage, wherein the first and second sets of circuitelements are resident in proximity to the location in the electroniccircuitry, wherein the first and second output voltages independentlyvary as a function of an operating temperature of the electroniccircuitry at the location, wherein the first and second output voltagesare not equal; a first current mirror circuit with a first input coupledto receive the first output voltage and a second input coupled toreceive the second output voltage, wherein the first current mirrorcircuit is configured to convert a difference between the first andsecond output voltages into a first voltage signal that is proportionalto the operating temperature; a second current mirror circuit with athird input coupled to receive the second output voltage, wherein thesecond current mirror circuit is configured to convert the second outputvoltage into a second voltage signal that is inversely proportional tothe operating temperature; and circuitry configured to determine thetemperature of the location in the electronic circuitry as a function ofa difference between the first and second voltage signals. The circuitryconfigured to determine the temperature of the location in theelectronic circuitry as the function of the difference between the firstand second voltage signals may include a first analog-to-digitalconverter configured to produce a first digital version of the firstvoltage signal, a second analog-to-digital converter configured toproduce a second digital version of the second voltage signal, andsubtraction circuitry configured to produce the difference between thefirst and second voltage signals as a function of a difference voltagevalue produced from a subtraction of the second digital version from thefirst digital version. The first and second analog-to-digital convertersmay be energized by one or more reference voltage sources that output areference voltage that fluctuates its magnitude as a function oftemperature. The first and second analog-to-digital converters may beenergized by a common reference voltage. The system circuitry configuredto determine the temperature of the location in the electronic circuitryas the function of the difference between the first and second voltagesignals may further include a first multiplexer with a first inputconfigured to receive the first voltage signal that is proportional tothe operating temperature, and a second input configured to receive thesecond voltage signal that is inversely proportional to the operatingtemperature, wherein an input of the first analog-to-digital converteris coupled to an output of the first multiplexer; a second multiplexerwith a first input configured to receive the second voltage signal thatis inversely proportional to the operating temperature, and a secondinput configured to receive the first voltage signal that isproportional to the operating temperature, wherein an input of thesecond analog-to-digital converter is coupled to an output of the secondmultiplexer; and selection circuitry configured to sequentially selectthe first and second inputs to the first and second multiplexers inorder to respectively produce first and second iterations of thedifference voltage value. The circuitry configured to determine thetemperature of the location in the electronic circuitry may be furtherconfigured to determine the temperature as a function of an average ofthe first and second iterations of the difference voltage value.

While these exemplary embodiments and aspects are described insufficient detail to enable those skilled in the art to practice theinvention, it should be understood that other embodiments may berealized and that various changes to the invention may be made withoutdeparting from the spirit and scope of the present invention. Thus, theprevious more detailed description is not intended to limit the scope ofthe invention, as claimed, but is presented for purposes of illustrationonly and not limitation to describe the features and characteristics ofthe present invention, to set forth the best mode of operation of theinvention, and to sufficiently enable one skilled in the art to practicethe invention. Accordingly, the scope of the present invention is to bedefined solely by the appended claims.

Though embodiments of the present invention are described utilizingPFETs, n-channel FETs (“NFETs”) could also be utilized by inverting thereceived selection signals. Naturally, other equivalent switchingdevices could also be utilized.

Within this description and the claims, the singular forms “a,” “an,”and “the” include plural referents unless the context clearly dictatesotherwise. The use of the word “a” or “an” when used in conjunction withthe term “comprising” in the claims and/or the specification may mean“one,” but it is also consistent with the meaning of “one or more,” “atleast one,” and “one or more than one.” The use of the term “or” in thisdescription and the claims is used to mean “and/or” unless explicitlyindicated to refer to alternatives only or the alternatives are mutuallyexclusive, although the disclosure supports a definition that refers toonly alternatives and “and/or.” Throughout this application, the terms“about” or “approximately” are used to indicate that a value includesthe inherent variation of error for the device, the method beingemployed to determine the value, or the variation that exists among thestudy subjects.

As will be appreciated by one skilled in the art, aspects of the presentinvention are described herein with reference to a flowchartillustration and block diagrams of methods, apparatus (systems), andcomputer program products according to embodiments of the invention(e.g., the flow diagram illustrated in FIG. 7 implemented with thecontrol logic block 418). Accordingly, aspects of the present inventionmay take the form of an entirely hardware embodiment, an entirelysoftware embodiment (including firmware, resident software, micro-code,etc.) or an embodiment combining software and hardware aspects that mayall generally be referred to herein as a “circuitry,” “module,” or“system.” Furthermore, aspects of the present invention may take theform of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon. It will be further understood that each block of the flowchartillustration and block diagrams, and combinations of blocks in theflowchart illustration and block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create circuitry configured to implement the functions/actsspecified in the flowchart and block diagram block or blocks. Thecomputer program instructions may also be loaded onto a computer, otherprogrammable data processing apparatus, or other devices to cause aseries of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and blockdiagram block or blocks.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (“RAM”), a read-only memory (“ROM”), an erasableprogrammable read-only memory (“EPROM” or flash memory), an opticalfiber, a portable compact disc read-only memory (“CD-ROM”), an opticalstorage device, a magnetic storage device, or any suitable combinationof the foregoing. In the context of this document, a computer readablestorage medium may be any tangible medium that can contain, or store aprogram for use by or in connection with an instruction executionsystem, apparatus, or device. Computer program code for carrying outoperations for aspects of the present invention may be written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++, or the likeand conventional procedural programming languages, such as the “C”programming language or similar programming languages.

What is claimed is:
 1. A system for determining a temperature of alocation in electronic circuitry, comprising: first circuitry, inproximity to the location in the electronic circuitry, configured toadjust first and second output voltages as a function of an operatingtemperature of the electronic circuitry at the location; secondcircuitry configured to convert the first and second output voltages toa first voltage signal that is proportional to the operatingtemperature; third circuitry configured to convert the second outputvoltage to a second voltage signal that is inversely proportional to theoperating temperature; fourth circuitry configured to determine adifference between the first voltage signal and the second voltagesignal to produce a difference voltage value, including: circuitryconfigured to produce a first digital version of the first voltagesignal, the circuitry configured to produce the first digital versionincludes a first analog-to-digital converter; circuitry configured toproduce a second digital version of the second voltage signal, thecircuitry configured to produce the second digital version includes asecond analog-to-digital converter; circuitry configured to produce adigital version of the difference voltage value from a differencebetween the first digital version of the first voltage signal and thesecond digital version of the second voltage signal, the circuitryconfigured to produce the difference voltage value includes subtractioncircuitry configured to receive the first and second digital versions;and fifth circuitry configured to determine the temperature of thelocation in the electronic circuitry as a function of the differencevoltage value.
 2. The system as recited in claim 1, wherein the secondcircuitry comprises a first current mirror circuit with a first inputcoupled to receive the first output voltage from the first circuitry anda second input coupled to receive the second output voltage from thefirst circuitry, wherein the first current mirror circuit is configuredto convert a difference between the first and second output voltagesinto the first voltage signal that is proportional to the operatingtemperature.
 3. The system as recited in claim 2, wherein the thirdcircuitry comprises a second current mirror circuit with a third inputcoupled to receive the second output voltage from the first circuitry,wherein the second current mirror circuit is configured to convert thesecond output voltage into the second voltage signal that is inverselyproportional to the operating temperature.
 4. The system as recited inclaim 1, wherein the first circuitry comprises: a first set of one ormore diodes having a first emitter injection area, the first set of theone or more diodes configured to output the first output voltage; and asecond set of one or more diodes having a second emitter injection area,the second set of the one or more diodes configured to output the secondoutput voltage, wherein the second emitter injection area is greaterthan the first emitter injection area.
 5. The system as recited in claim1, wherein the temperature of the location in the electronic circuitryis determined as a function of the digital version of the differencevoltage value.
 6. The system as recited in claim 1, wherein the firstand second analog-to-digital converters are energized by a commonreference voltage.
 7. The system as recited in claim 1, wherein thefourth circuitry further comprises: a first multiplexer with a firstinput configured to receive the first voltage signal that isproportional to the operating temperature, and a second input configuredto receive the second voltage signal that is inversely proportional tothe operating temperature, wherein an input of the firstanalog-to-digital converter is coupled to an output of the firstmultiplexer; a second multiplexer with a first input configured toreceive the second voltage signal that is inversely proportional to theoperating temperature, and a second input configured to receive thefirst voltage signal that is proportional to the operating temperature,wherein an input of the second analog-to-digital converter is coupled toan output of the second multiplexer; and selection circuitry configuredto sequentially select the first and second inputs to the first andsecond multiplexers in order to respectively produce first and seconditerations of the difference voltage value.
 8. The system as recited inclaim 7, wherein the fifth circuitry is configured to determine thetemperature of the location in the electronic circuitry as a function ofan average of the first and second iterations of the difference voltagevalue.
 9. The system as recited in claim 7, wherein the fourth circuitryfurther comprises: a third multiplexer with a first input coupled to anoutput of the first analog-to-digital converter, a second input coupledto an output of the second analog-to-digital converter, and an outputcoupled to a first input of the subtraction circuitry; and a fourthmultiplexer with a first input coupled to an output of the secondanalog-to-digital converter, a second input coupled to an output of thefirst analog-to-digital converter, and an output coupled to a secondinput of the subtraction circuitry, wherein the selection circuitry isconfigured to sequentially select the first and second inputs to thefirst, second, third, and fourth multiplexers in order to produce the atleast first and second iterations of the difference voltage value.
 10. Amethod for determining a temperature of a location in electroniccircuitry, comprising: converting a first voltage signal that isproportional to the temperature of the location in the electroniccircuitry to a first digital value; converting a second voltage signalthat is inversely proportional to the temperature of the location in theelectronic circuitry to a second digital value; determining a firstdifference value between the first and second digital values; andoutputting the temperature of the location in the electronic circuitryas a function of the first difference value between the first and seconddigital values, wherein the converting of the first and second voltagesignals is performed with first and second analog-to-digital convertersenergized with a common reference voltage.
 11. The method as recited inclaim 10, wherein the first voltage signal that is proportional to thetemperature of the location in the electronic circuitry is a differencebetween first and second voltages.
 12. The method as recited in claim10, further comprising: converting the first voltage signal that isproportional to the temperature of the location in the electroniccircuitry to a third digital value; converting the second voltage signalthat is inversely proportional to the temperature of the location in theelectronic circuitry to a fourth digital value; determining a seconddifference value between the third and fourth digital values; andoutputting the temperature of the location in the electronic circuitryas a function of an average of the first and second difference values.13. A system for determining a temperature of a location in electroniccircuitry, comprising: a first set of circuit elements configured tooutput a first output voltage; a second set of circuit elementsconfigured to output a second output voltage, wherein the first andsecond sets of circuit elements are resident in proximity to thelocation in the electronic circuitry, wherein the first and secondoutput voltages independently vary as a function of an operatingtemperature of the electronic circuitry at the location, wherein thefirst and second output voltages are not equal; a first current mirrorcircuit with a first input coupled to receive the first output voltageand a second input coupled to receive the second output voltage, whereinthe first current mirror circuit is configured to convert a differencebetween the first and second output voltages into a first voltage signalthat is proportional to the operating temperature; a second currentmirror circuit with a third input coupled to receive the second outputvoltage, wherein the second current mirror circuit is configured toconvert the second output voltage into a second voltage signal that isinversely proportional to the operating temperature; and circuitryconfigured to determine the temperature of the location in theelectronic circuitry as a function of a difference between the first andsecond voltage signals, including: a first analog-to-digital converterconfigured to produce a first digital version of the first voltagesignal; a second analog-to-digital converter configured to produce asecond digital version of the second voltage signal; and subtractioncircuitry configured to produce the difference between the first andsecond voltage signals as a function of a difference voltage valueproduced from a subtraction of the second digital version from the firstdigital version.
 14. The system as recited in claim 13, wherein thefirst and second analog-to-digital converters are energized by one ormore reference voltage sources that output a reference voltage thatfluctuates its magnitude as a function of temperature.
 15. The system asrecited in claim 13, wherein the first and second analog-to-digitalconverters are energized by a common reference voltage.
 16. The systemas recited in claim 15, wherein the circuitry configured to determinethe temperature of the location in the electronic circuitry as thefunction of the difference between the first and second voltage signalsfurther comprises: a first multiplexer with a first input configured toreceive the first voltage signal that is proportional to the operatingtemperature, and a second input configured to receive the second voltagesignal that is inversely proportional to the operating temperature,wherein an input of the first analog-to-digital converter is coupled toan output of the first multiplexer; a second multiplexer with a firstinput configured to receive the second voltage signal that is inverselyproportional to the operating temperature, and a second input configuredto receive the first voltage signal that is proportional to theoperating temperature, wherein an input of the second analog-to-digitalconverter is coupled to an output of the second multiplexer; andselection circuitry configured to sequentially select the first andsecond inputs to the first and second multiplexers in order torespectively produce first and second iterations of the differencevoltage value.
 17. The system as recited in claim 16, wherein thecircuitry configured to determine the temperature of the location in theelectronic circuitry is further configured to determine the temperatureas a function of an average of the first and second iterations of thedifference voltage value.